Automobile and the like commonly have locking devices in their doors or other areas which can be unlocked only with a proper key, and an engine that can be started using a proper ignition key. In this manner, attempts are made to prevent vehicle theft. For more secure theft prevention, further theft prevention mechanisms have been proposed and are being implemented.
For example, in Automobile Technique Application Publications No. 95603 (Association of Japan Automobile Industry, Intellectual Property Section, published on Dec. 1, 1995), a vehicle theft preventing device for prohibiting engine start when an improper ignition key is used is disclosed.
In this vehicle theft preventing device, a transponder for transmitting a key code is installed in an ignition key. This transponder receives power from a radio wave transmitted from an antenna set in a key cylinder, and transmits the key code stored therein. An immobilizer ECU (Electronic Control Unit) is connected to the antenna in the key cylinder, and the immobilizer ECU judges whether or not the key code sent from the transponder is correct. The immobilizer ECU has a connection to an engine ECU which controls engine ignition and fuel injection. The immobilizer ECU notifies the engine ECU of whether or not the correct key code has been received. When the immobilizer ECU has not received, the correct key code, the engine ECU prohibits fuel injection and engine ignition, and executes engine stopping control. In this manner, engine start and vehicle motion can be prevented when an improper key is used to start the engine. On this occasion, the engine ECU starts the engine as usual when ignition is switched ON by an operation using an ignition key, and stopped the engine after receiving a signal from the immobilizer ECU.
The immobilizer ECU only controls the engine ECU. Therefore, it is possible to incorporate the function of an immobilizer ECU in an engine ECU, and the function of the immobilizer ECU can be achieved by a single ECU. On the other hand, the immobilizer function is not presently installed in all vehicles, and a large number of vehicles do not have this function. However, as an ECU is created as a semiconductor integrated circuit, it has been desired that ECUs be generalized as much as possible. Therefore, it is considered to be preferable that the immobilizer function be installed in all engine ECUs and that the availableness or unavailableness of this function can be set. In this manner, generality of an ECU is improved while individual vehicle requests can be dealt with.
However, in the ECU whose immobilizer function availableness can be set, the immobilizer function is not demonstrated when the setting is changed. Therefore, the setting should be unchangeable. Nevertheless, even when the setting cannot be changed, an engine can be started if an ECU with the immobilizer function is detached from a vehicle and an ECU from a vehicle without the immobilizer function is attached in its place. Furthermore, in a brand-new ECU (a virgin ECU), information regarding availableness or unavailableness of the immobilizer function is not written. It is therefore possible for an engine to be started if such a virgin ECU is attached to a vehicle instead of the vehicle's original ECU with the immobilizer function.
The present invention has been created to solve the above problems. The present invention is an engine start controlling device which stores information regarding availableness or unavailableness of the immobilizer function, and an object of the present invention is to provide an engine start controlling device which can achieve the appropriate immobilizer function.